Surrounding the waters and wetlands of San Francisco Bay are a variety of 'upland' habitats including the five most common types – coastal scrub-chaparral, coniferous-redwood forests, grasslands, oak woodlands, and riparian (streamside) forests. These vegetation communities vary in their mix of native and non-native plant species and the composition of bird communities they support.
Each upland type was assigned a suite of indicator species that best represent that habitat in the Bay Area. Over the 42 years of study:
Indicators for riparian birds show an increase of greater than 20%. Riparian habitats are recognized as one of the most important upland habitat types in the West for birds and other wildlife. Streams were heavily impacted in the past. In response to the listing of imperiled salmonids and concern for water quality, stream restoration has increased dramatically over the past several decades, benefiting birds as well.
Indicators for oak woodland and coniferous-redwood forest birds are stable.
Coastal scrub-chaparral and grassland birds are declining, coastal scrub by 27% and grassland by over 45%. Species in these habitat types continue to be impacted by loss and degradation of habitat. These trends are consistent with the declining trend found in the National State of the Birds Report, 2009.
Primary threat: Habitat loss and degradation caused by land-use changes such as open space conversion to housing or intensive agriculture, invasions of non-native species, and lack of ecological disturbances such as fire. For example, the two habitat types with the greatest bird declines, coastal scrub-chaparral and grasslands, are transitioning to other habitat types due to lack of disturbance and the invasion of native species (such as Douglas fir), non-native plant species (such as broom), and annual grasses that alter fire regimes.
Lack of appreciation for the habitat value of scrub-chaparral and grasslands. Not typically thought of as beautiful or in need of protection, scrub-chaparral is seen as an eyesore or fire hazard, and a "clear the brush" attitude reduces habitat.
Climate change affects vegetation type and water availability, thereby altering the amount, type, and quality of habitats available to birds.
Gaps in scientific knowledge that is needed to inform and evaluate land management decisions and policy actions.
Planning, Management, Restoration:
Adopt and implement the Uplands Habitat Goals and Bay Area Critical Linkages documents: www.bayarealands.org.
Control the most destructive invasive species, and support and participate in the Bay Area Early Detection Network (www.baedn.org).
Use disturbance (e.g., fire and grazing) to create and maintain diverse upland habitats.
Promote conservation on private lands, including thorough use of economic incentive programs.
Continue to restore riparian areas.
Promote wise water use in order to maintain stream flows and groundwater recharge.
Educate the public on the value of habitats such as coastal scrub-chaparral and grasslands.
Determine which species are most vulnerable to the effects of climate change.
Map future distributions of species under climate change and land use change scenarios.
Monitor upland birds to track distribution and abundance changes and nest success and survival.
Identify Bay Area species population targets, working with the San Francisco Bay Joint Venture.
Study the use of grazing and other disturbances as vegetation management tools.